Made changes to IsTree, added tests.
Merge remote-tracking branch 'upstream/master'

Pull next batch of updates to documentation.
Merged, started modifying functions 20-39
Finished reviewing functions 21-27
Updated documentation up to function 67
Merge remote-tracking branch 'upstream/master'

Merge with upstream.
Revised doc for functions 68-77
Finished tests up to function 27
Merge remote-tracking branch 'upstream/master'

Merge changes with upstream.
Made functions 45 and 46 consistent with each other.
Merge remote-tracking branch 'upstream/master'

Merge with upstream.